Apparatus and method for measuring electrical energy consumption

ABSTRACT

A current transformer is connected to an electrical power circuit to provide a measure of the current in the power circuit. The current measure is applied through a reversing switch and a diode rectifying bridge to a coulombmeter and is controlled by commutating the bridge with a voltage from a voltage transformer connected to the electrical power circuit. The connections are made to apply current to the coulombmeter during the portion of the current cycle that occurs during a selected voltage half cycle. The current measure is further controlled by a modulating circuit connected to respond to the voltage of the power circuit and to pulse modulate the current as a function of voltage level. A control means responds to a selected condition of the coulombmeter to reverse the control current connections to the coulombmeter. A reading means senses the number of reversal operations to thereby provide an indication of the total amount of energy consumed in the power circuit over a selected period.

United States Patent [451 June 27, 1972 Riebs Primary Examiner-Alfred E.Smith Attorney-R. J. Falkowski [5 7] ABSTRACT A current transformer isconnected to an electrical power circuit to provide a measure of thecurrent in the power circuit. The current measure is applied through areversing switch and a diode rectifying bridge to a coulombmeter and iscontrolled by commutating the bridge with a voltage from a voltagetransformer connected to the electrical power circuit. The

connections are made to apply current to the coulombmeter during theportion of the current cycle that occurs during a selected voltage halfcycle. The current measure is further controlled by a modulating circuitconnected to respond to the voltage of the power circuit and to pulsemodulate the cur rent as a function of voltage level. A control meansresponds to a selected condition of the coulombmeter to reverse thecontrol current connections to the coulombmeter. A reading means sensesthe number of reversal operations to thereby provide an indication ofthe total amount of energy consumed in the power circuit over a selectedperiod.

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CNTRL 54 MNS 65 53 COULOMBMETER FIG. 4

2 GI 62 l fi 57 ML) 58 INVENTOR. RICHARD E. RIEBS 5 M ATTORNEY 43 MNS[nous i APPARATUS AND METHOD FOR MEASURING ELECTRICAL ENERGY CONSUMPTIONThis invention relates to electrical power measuring systems,particularly to static watt-hour meter systems for measuring energyconsumption in an alternating electrical power circuit.

The measurement of electrical energy consumed in alternating currentpower circuits presently is usually accomplished with standard inductiontype watt-hour meters. Static watt-hour meters using relatively recentlydeveloped semiconductor electronic components, such as transistors anddiodes, are generally recognized as having many better characteristicsthan induction meters. However, static watt-hour meters produced havebeen relatively expensive, relatively unreliable, and difficult tocalibrate. A static watt-hour meter as shown in highly reliable,relatively inexpensive, and readily adaptable to reading by moderncomputer-type accounting systems. However, the compensation for thevoltage variations must be provided to achieve the desirable accuracy.With this invention an accurate, simple and reliable modulating meanscompensates for voltage variations.

According to this invention a current proportional to the current in analternating electrical power circuit is rectified and applied to acurrent measuring and integrating device and continuously modified as afunction of the phase relationship between the voltage and current,thereby automatically compensating for the phase angle between voltageand current. To compensate for differences in voltage levels the currentto the measuring device is pulse modulated as a function of the voltagelevel so that an accurate indication accounting for current, phaseangle, and voltage is provided. A coulombmeter is used that accuratelyindicates total charge received which is proportional to energy consumedin the power circuit. The charge received is sensed and the currentreversed when the coulombmeter has reached its storage capacity in onedirection to charge the coulombmeter in an opposite direction. The totalreversals are recorded to provide an indication of total power consumedby the power circuit over a selected period of time.

Other objects and advantages of this invention will be apparent from thefollowing detailed description.

FIG. I is a schematic and block diagram of a watt-hour meter systemaccording to this invention;

FIG. 2 is a graph of three wave forms that may occur during theoperation of the system shown in FIG. 1;

FIG. 3 is a graph of another wave form that may occur in the circuit ofFIG. 1;

FIG. 4 is a side view of a coulombmeter of a type that may be utilizedwith the circuit shown in FIG. 1;

FIG. 5 is a schematic and block diagram of another watthour meter systemaccording to this invention; and

FIG. 6 is a drawing of a coulombmeter and a schematic of a reversingswitch network and indicating device that could be utilized with thecircuits shown in FIGS. 1 and 5.

Referring to FIG. 1, an electrical power circuit 10 comprises anelectrical power source 11 and a load 12 connected to the power sourceby conductors 13 and 14. An alternating electrical energy measuringsystem for measuring the electrical energy consumed by load 12 comprisesa current means responsive to the current in power circuit 10 forproducing a control current varying as a function of the power circuitcurrent, a phase angle means 40 responsive to the voltage in electricalcircuit 10 for modifying the control current as a function of the phaseangle between the voltage and current of power circuit 10, and a voltagemeans responsive to the voltage in power circuit 10 for modifying thecontrol current as a function of the power circuit voltage. The outputfrom the power sensing means is applied to a recording means 50 forreading and indicating the total energy consumed by power circuit 10.

Referring to FIG. 1, current means 20 comprises a current transformer 21connected to sense the current in conductor 14 and load 12. Thecharacteristics of current transformer 21 are selected to provide acontrol current at a level desirable for the circuit components at theanticipated currents of the power circuit. The current means isresponsive to the current in the electrical power circuit to produce acontrol current varying as a function of the power circuit current andat a selected phase angle to the power circuit current. In typicalapplications the control current is proportional to and substantially inphase with the power circuit current. The control current is deliveredto recording means 50 along conductors 22 and 23.

The control current is modified by phase angle means 40 to compensatefor any difference in phase angle between the voltage and current inpower circuit 10. The phase angle means comprises a voltage transformer41 having a primary winding 41p connected between conductors l3 and 14and a secondary output winding 41s. Voltage transformer 41 is selectedto produce a control voltage at a level varying as a function of thepower circuit voltage and at a preselected phase angle relative to thevoltage in circuit 10. In typical applications the control voltage issubstantially proportional to and substantially in phase with theelectrical circuit voltage and at a level selected to provide reliableoperation of the system. The phase angle means also comprises a resistor42 and a rectifying bridge 43 comprising diodes 43a, 43b, 43c and 43dconnected to voltage transformer with conductors 47 and 48.

Voltage means 30 is connected to the power circuit to obtain a levelcontrol voltage varying as a function of the voltage level in the powercircuit from voltage transformer 41. The voltage means modifies ormodulates the control current as a function of the power circuit voltagein response to the level control voltage which appears at secondarywinding 41:. The voltage means comprises a voltage sensing means forproducing the level control voltage varying as a function of the loadvoltage level, a current control means for controlling the applicationof the control current to the recording means in response to anelectrical signal input having a preselected level, a biasing means forbiasing the current control means to stop the application of controlcurrent to the recording means, and a pulse modulating means responsiveto the level of the control voltage for controlling the biasing means topulse modulate the biasing means to apply control current pulses to therecording means at a rate substantially proportional to the level of thecontrol voltage.

The voltage sensing means comprises voltage transformer 41 whichproduces the control voltage across output winding 41s. The controlvoltage is rectified by a rectifying bridge 31 comprising diodes 31a,31b, 31c and 31d and received from output winding 41s through a resistor32. The rectified control voltage is applied to the biasing means andthe pulse modulating means. The biasing means comprises a resistor 39connected to continuously apply a positive input to bridge 43 through adiode 45.

The pulse modulating means comprises a multivibrator circuit having aresistor 35, a capacitor 34, an inductance 37, a Shockley diode 36, anda Zener diode 38; and a shunting circuit having a transistor 44 and abase resistor 46.

Recording means 50 comprises a measuring means for indicating electricalenergy received and a reading means 53 for reading the total electricalenergy received by the measuring means. The measuring means comprises ameasuring or current integrating device, such as a mercury plating cellor coulombmeter 51, and a control means 56 for sensing the indicationprovided by coulombmeter 51 and for controlling the polarity of thecontrol current connection. The control means comprises a means forreversing the direction of the control current applied to coulombmeter51, such as a reversing switch 52, and a sensing means for sensing theindication produced by coulombmeter 51, as indicated by dashed line 65,and for controlling the reversing means, as indicated by dashed line 55.Coulombmeter 51 may be any suitable device that integrates current as afunction of time, for example, a mercury plating cell coulombmeter 51 asshown in FIG. 4, a capacitor, or the coulombmeter shown in FIG. 6.Reading means 53 may be of any type known in the art that could comprisea counter or similar device for indicating the number of reversals ofcurrent applied to coulombmeter 51 to provide an appropriate output asindicated by line 54.

Referring to FIG. 4, coulombmeter 51 is a mercury plating cell of a typecommercially available and comprises a sealed glass envelope 62,electrodes 63 and 64, typically of nonreactive metal such as platinum,connected to conductors 57 and 58, respectively. A mercury plating cell59 is enclosed within envelope 62 and has a mercury section 59a and amercury section 59b separated by an electrolyte section 61, using anysuitable electrolyte such as a mercuric iodide salt solution. As currentis applied to the cell the mercury is moved from one mercury section tothe other as a function of current level and direction in a manner knownin the art.

Referring to FIG. 1, with a coulombmeter as shown in FIG. 4, the sensingmeans senses the potential across coulombmeter 51 in any manner known inthe art, as indicated by dashed line 65. When mercury has beensubstantially removed from one mercury section, the potential acrosscoulombmeter 51 rises significantly, and the sensing means senses thisincreased potential in any manner known in the art and operatesreversing switch 52 to reverse the polarity of the connections alongconductors 22 and 23. In addition, reading means 53 responds to theincreased potential or to the reversal function to indicate in somereadout form known in the art along line 54, either by counting or othermeans, the fact that one selected unit of electrical energy has beenconsumed as indicated by the transfer of mercury in the mercury cellfrom one mercury section to the other.

Referring to FIG. 6, a type of measuring device and control means thatmay be used has a coulombmeter 70 with a double curve tube or envelope71 as shown with a mercury cell 72 having a mercury section 720 and amercury section 72b separated by a suitable electrolyte section 73.Current electrodes 74 and 75 carry control current from the rest of themeter system along conductors 22' and 23', corresponding to conductors22 and 23 shown in FIG. 1, through a reversing switch 78. Sensingelectrodes 81 and 82 are positioned within envelope 71 to sense thetransfer of a selected amount of mercury between mercury cell sections72a and 72b to thereby indicate a selected amount of electrical currentreceived by or passed through coulombmeter 70.

Reversing switch 78 is connected between coulombmeter 70 and conductors22 and 23. A power source, such as a battery 83, a double-pole,double-throw, double-acting latch relay comprising a relay winding 85, arelay winding 86, switch input terminals 87a and 87b, and switch outputterminals 88a, 88b, 88c and 88d. The reading means comprises a counter89 of any type known in the art and a current transformer 92 connectedto be responsive to current through a conductor 91 to indicate each timea reversal occurs.

In the operation of the circuit shown in FIG. 6, as the direct controlcurrent is applied along conductors 22' and 23, assuming the conditionof mercury cell 72 to be as shown, and assuming a negative polarity atconductor 23', the current path is from conductor 23, through switchinput terminal 87b and output terminal 880, a conductor 93, electrode74, mercury cell 72, thereby applying current in a direction to movemercury section 72b to 72a, electrode 75, a conductor 94, switch outputterminal 880 and input terminal 87a to conductor 22'. The amount ofmercury in section 72a is increased as a function of current applied andthe level of the mercury in section 72a rises while the level in section72b falls.

As the plating action continues, the amount of mercury in section 72aincreases until the mercury reaches a level to make contact with sensingelectrode 81. Upon contacting electrode 81, a circuit is closed betweensensing electrode 81 and electrode 74 and a current path from battery 83is completed through relay winding 86 to activate winding 86 and operatereversing switch 78 to take the other position from that shown in FIG. 6to reverse the direction of control current to coulombmeter 70. Thecurrent path for the operation of relay winding 86 is from battery 83through conductors 91 and 23, switch input terminal 87b and outputterminal 880, conductor 93, electrode 74, the mercury between electrodes74 and 81, electrode 81, and relay winding 86 to battery 83. Thisenergizes winding 86 and moves the switch contacts to connect inputterminals 87a and 87b to output terminals 88b and 88d, respectively. Thecurrent through conductor 91 provides a current pulse in currenttransformer 92 that is sensed by counter 89 indicating that a reversalhas taken place. Upon the reversal of switch 78, relay winding 86 isde-energized as the current path from battery 83 is broken by thedisconnection of switch input terminal 88b from output terminal 880.

Upon reversal of the switch, currentpolarity is reversed and mercurysection 72b receives mercury until the circuit between sensing electrode82 and electrode 75 is closed. The current path for plating mercury cell72 is from conductor 22 through switch input terminal 87a and outputterminal 88b, conductor 93, electrode 74, mercury cell 72, electrode 75,conductor 94, switch output terminal 88d and input terminal 87b toconductor 23. When the mercury in mercury section 72b reaches electrode82, a circuit is completed between sensing electrode 82 and currentelectrode 75 and winding is energized to move the switch contacts backto the position shown in FIG. 6. The current path is from battery 83through conductors 91 and 23', switch input terminal 87b and outputterminal 88d, conductor 94, electrode 75, the mercury between electrodes75 and 82, sensing electrode 82, a conductor 95, and relay winding 85 tobattery 83. The current switching the relays is sensed by counting means89 and relay winding 85 is de-energized as the circuit is broken by theswitch contacts between switch input terminal 87a and output terminal88b.

In the operation of the circuit shown in FIG. 1, the control current isapplied from current transformer 21 to recording means 50 as controlledby rectifying bridge 43. Referring to FIG. 2, FIG. 2B shows a typicalcontrol current wave form of current to reversing switch 52 withoutmodification. Since the current is alternating, no charge wouldaccumulate on coulombmeter 51 because the polarity is reversed everycycle. However, by controlling bridge 43 with the phase control voltagefrom secondary winding 41: of transformer 41, bridge 43 acts as a shortcircuit to the control current whenever bridge 43 is forward biased bythe phase control voltage. When the voltage at a conductor 47 ispositive relative to a conductor 38, bridge 43 is .forward biased and nocontrol current is passed to coulombmeter 51. The polarity relationshipof the voltage of secondary winding 41: and current transformer 21 isselected to make conductor 47 positive with the control voltage fromtransformer 41 and conductor 22 negative with the control current fromtransformer 21 when the voltage and current are in phase.

Assuming a phase control voltage wave form as shown in FIG. 2A and acontrol current wave form as shown in FIG. 2B lagging the voltage about30, control current is applied to the coulombmeter only during thepositive half cycle of the phase control voltage. With the controlvoltage out of phase with the control current, an automatic compensationfor the phase angle, and thus actual energy consumed, is made sinceenergy consumed is equal to the product of the voltage, current and thecosine of the phase angle. The net electrical current received by andpassed through the coulombeter, as shown in FIG. 2C, is the currentduring the positive portion of the current wave form shown in FIG. 2Cminus the negative portion. This sum varies as a function of the productof the voltage, current, and cosine of the phase angle and, thus,permits easy calibration of the meter system. When the phase controlvoltage and control current are in phase, rectifying bridge 43 conductsduring the positive half cycle of the voltage and the total half cyclecontrol current is applied to coulombmeter 51. As the control phaseangle changes the commutation on rectifier bridge 43 changes and currentflows for a portion of the current cycle in one direction and during theremainder in the other direction, thereby automatically compensating fora reading of the actual energy consumed.

Voltage means 30 modulates the control current still further. Voltagemeans 30 receives a level control voltage from secondary winding 41s oftransformer 41 and rectifies the voltage with rectifying bridge 31. Thisrectified voltage is then applied-to multivibrator circuit 33 to pulsemodulate the control current by further controlling the commutation ofrectifier bridge 43. Referring to FIG. 3, a circuit of the type shown ata selected voltage level would modulate the control current as shown inFIG. 2C to a form shown in FIG. 3.

In operation of voltage means 30, the rectified voltage is appliedthrough resistor 35, resistor 39, and diode 45 to conductor 47 toforward bias bridge 43 and thereby prevent the control current frombeing applied to coulombmeter 51. This rectified voltage is shunted awayfrom bridge 43 whenever transistor 44 is turned on. With transistor 44turned on, control current will be applied to coulombmeter 51 unlessconductor 47 is made positive by the phase control voltage applied toconductor 47 through resistor 42 directly from transformer 41.Transistor 44 is controlled by the operation of the circuitmultivibrator made up of resistor 46, capacitor 34, inductance 37,Shockley diode 36, and Zener diode 38. The multivibrator has thecharacteristic of producing a higher pulse rate as the input voltageincreases because the charge is more quickly accumulated on capacitor 34to break over Shockley diode 36. When the charge on capacitor 34 breaksover diode 36, a voltage appears across resistor 46 and base currentturns on transistor 44 and connects the collector of transistor 44 toconductor 48 to enable conductor 47 to go negative across diode 45 if itis negative because of the voltage applied directly from winding 41s.The rate of tum-on of transistor 44 is determined by the rate at whichcapacitor 34 reaches the breakdown voltage of diode 36. Thus, transistor44 is turned at a rate dependent upon the voltage level. Appropriatecalibration and correlation of the voltage level is made to the systemto adjust for different voltage levels. Zener diode 38 is connected tomaintain a positive potential across capacitor 34 and prevent fulldischarge of capacitor 34. If capacitor 34 were allowed to fullydischarge, current through resistor 39 could be interrupted upon theinitiation of a charge cycle of capacitor 34.

Inductance 37 provides a frequency control component for insuringaccurate modulation, and diode 45 prevents the shunting of the positivevoltage occurring when conductor 47 is made positive by the positivehalf cycle appearing at secondary winding 41s of transformer 41.

Referring to FIG. 5, a circuit similar to that of FIG. 1 is shown inwhich corresponding components are indicated by corresponding primednumerals. The circuit shown in FIG. 5 comprises an electrical powercircuit a current measuring means a phase angle means 40', a voltagemeans and a recording means 50. The circuits of FIG. 1 and FIG. 5 aresubstantially the same except that a transistor commutating circuit 143is substituted for rectifying bridge 43 shown in FIG. I. Commutatingcircuit 143 comprises a transistor 144 and a transistor 145 connectedacross conductors 22 and 23' to shunt the controlcurrent from currenttransformer 21 In the operation of the circuit shown in FIG. 5 thecommutator action is produced by the shorting of coulombmeter 51 bytransistor 144 and transistor 145 whenever conductor 47' fromtransformer 41 is positive, in which case positive current flows fromsecondary winding 41.x through 42' and conductor 47 to the base oftransistor 145, through the emitters of transistors 144 and 145 to thebase of transistor 144, through conductor 48', and back through diode31d of rectifier bridge 31'. Thus, control current from currenttransformer 21' is not applied to coulombmeter 51 during one-half cycleof the voltage cycle appearing at secondary winding 41: of voltagetransformer 41 However, when conductor 47' is negative there is no basecurrent to transistor 145, and transistor 145 and transistor 144 do notconduct from this source. However, a source of base current fortransistor 145 is applied from rectifier bridge 31' through resistorresistor 39 and diode to the base of transistor 145. This prevents theapplication of control current to coulombeter except when transistor isturned on to shunt this current away from base of transistor 44 in thesame manner as described with respect to FIG. I.

I claim:

1. An electrical power measuring system for measuring the electricalenergy consumed by an electrical load comprising:

a current means responsive to the load current for producing a controlcurrent varying as a function of said load current;

a recording means connected to receive the control current for measuringelectrical current received;

a current control means connected between the current means and therecording means and responsive to an electrical input for controllingapplication of said control current to said recording means to applycontrol current to said recording means only when said electrical inputis below a preselected level;

a voltage sensing means responsive to the load voltage for producing acontrol voltage varying as a function of the level of said load voltage;

a biasing means for continuously applying an electrical input above saidpreselected level to the current control means; and

a pulse modulating means responsive to the control voltage for pulsemodulating the electrical input of said biasing means to a level belowthe preselected level at a pulse rate varying as a function of the levelof said control voltage.

2. An electrical power measuring system according to claim 1 formeasuring electrical energy consumed in an alternating electrical powersystem also comprising a phase angle means for applying an electricalinput above the preselected level during a selected portion of eachcycle of the control voltage to the current control means.

3. An alternating electrical power measuring system according to claim 2wherein said pulse modulating means is responsive to the average controlvoltage level to shunt the electrical input from the biasing means andthe electrical input from the phase angle means at a pulse ratesubstantially proportional to said average control voltage level.

4. An alternating electrical power measuring system according to claim 3wherein said current control means comprises a commutating circuitconnected between the current means and the recording means andresponsive to an electrical input above the preselected level to shuntsaid control current away from said recording means.

5. An alternating electrical power measuring system according to claim 4wherein said current means is responsive to the load current to producea control current substantially proportional to said load current.

6. An alternating electrical power measuring system according to claim 5wherein said recording means comprises a current measuring andintegrating device.

7. An electrical power measuring system according to claim 1 whereinsaid pulse modulating means comprises a multivibrator and shuntingcircuit connected to intermittently shunt the control current at a pulserate varying as a function of the level of said control voltage.

8. An electrical power measuring system according to claim 1 whereinsaid pulse modulating means is responsive to the control voltage levelto shunt the electrical input to the current control means from thebiasing means at a pulse rate substantially proportional to the level ofsaid control voltage.

9. An electrical power measuring system according to claim 1 whereinsaid current control means comprises a commutating circuit connectedbetween the current means and the recording means and responsive to theelectrical input to shunt said control current away from said recordingmeans when said electrical input is above the preselected level.

10. An electrical power measuring system according to claim 1 whereinsaid current means is responsive to the load current to produce acontrol current substantially proportional to said load current.

11. An electrical power measuring system according to claim 10 formeasuring energy consumption in an alternating electrical load circuitalso comprising a phase angle means for applying an electrical inputabove the preselected level during a selected half cycle of said controlvoltage to the current control means.

12. An alternating electrical power measuring system according to claim11 wherein said voltage sensing means is responsive to the load voltageto produce a control voltage substantially proportional to said loadvoltage.

13. An alternating electrical power measuring system according to claim12 wherein said pulse modulating means is responsive to the controlvoltage level to shunt the electrical input from the biasing means andfrom the phase angle means at a rate substantially proportional to saidcontrol voltage level.

14. An alternating electrical power measuring system according to claim13 wherein said recording means comprises a current measuring andintegrating device.

15. An alternating electrical power measuring system according to claim14 wherein said pulse modulating means comprises a multivibrator andshunting circuit connected to pulse modulate the electrical input fromthe biasing means and from the phase angle means by intermittentlyshunting said electrical inputs at a rate varying substantiallyproportionally to the average level of said control voltage.

16. An electrical power measuring system according to claim 10 whereinsaid current control means comprises a controllable commutating deviceresponsive to the electrical input and connected to shunt said controlcurrent, and wherein said pulse modulating means is connected to shuntsaid electrical input at a pulse rate substantially proportional to theaverage level of said control voltage.

17. An electrical power measuring system according to claim 16 formeasuring energy consumption in an alternating electrical load circuitalso comprising a phase angle means for applying an electrical inputabove the preselected level during a selected half cycle of the controlvoltage to the current control means.

18. An alternating electrical power measuring system according to claim17 wherein said recording means comprises a current measuring andintegrating device.

19. An alternating electrical power measuring system for measuring theelectrical energy consumed by an electrical load comprising:

a current transformer connected to be responsive to the load current toproduce a control current as an output;

a current measuring and integrating device connected to receive thecontrol current;

a commutating circuit connected between the current transformer and themeasuring device and responsive to an electrical input of one polarityto shunt said control current;

a biasing means for continuously applying an electrical input havingsaid one polarity to the commutating circuit;

a voltage transformer connected to be responsive to the load voltage toproduce a control voltage as an output;

a multivibrator shunting circuit having a pulse rate proportional to thelevel of an input and connected to shunt the electrical input to thecommutating circuit; and

a rectifying bridge connected to rectify the control voltage and applythe rectified control voltage as an input to the multivibrator shuntingcircuit.

20. An alternating electrical power measuring system according to claim19 also comprising a phase angle means for applying the control voltageas an electrical input to the commutating circuit to thereby shunt thecontrol current during the one polarity portion of said control voltage,and wherein said multivibrator shunting circuit also shunts said controlvoltage.

1. An electrical power measuring system for measuring the electricalenergy consumed by an electrical load comprising: a current meansresponsive to the load current for producing a control current varyingas a function of said load current; a recording means connected toreceive the control current for measuring electrical current received; acurrent control means connected between the current means and therecording means and responsive to an electrical input for controllingapplication of said control current to said recording means to applycontrol current to said recording means only when said electrical inputis below a preselected level; a voltage sensing means responsive to theload voltage for producing a control voltage varying as a function ofthe level of said load voltage; a biasing means for continuouslyapplying an electrical input above said preselected level to the currentcontrol means; and a pulse modulating means responsive to the controlvoltage for pulse modulating the electrical input of said biasing meansto a level below the preselected level at a pulse rate varying as afunction of the level of said control voltage.
 2. An electrical powermeasuring system according to claim 1 for measuring electrical energyconsumed in an alternating electrical power system also comprising aphase angle means for applying an electrical input above the preselectedlevel during a selected portion of each cycle of the control voltage tothe current control means.
 3. An alternating electrical power measuringsystem according to claim 2 wherein said pulse modulating means isresponsive to the average control voltage level to shunt the electricalinput from the biasing means and the electrical input from the phaseangle means at a pulse rate substantially proportional to said averagecontrol voltage level.
 4. An alternating electrical power measuringsystem according to claim 3 wherein said current control means comprisesa commutating circuit connected between the current means and therecording means and responsive to an electrical input above thepreselected level to shunt said control current away from said recordingmeans.
 5. An alternating electrical power measuring system according toclaim 4 wherein said current means is responsive to the load current toproduce a control current substantially proportional to said loadcurrent.
 6. An alternating electrical power measuring system accordingto claim 5 wherein said recording means comprises a current measuringand integrating device.
 7. An electrical power measuring systemaccording to claim 1 wherein said pulse modulating means comprises amultivibrator and shunting circuit connected to intermittently shunt thecontrol current at a pulse rate varying as a function of the level ofsaid control voltage.
 8. An electrical power measuring system accordingto claim 1 wherein said pulse modulating means is responsive to thecontrol voltage level to shunt the electrical input to the currentcontrol means from the biasing means at a pulse rate substantiallyproportional to the level of said control voltage.
 9. An electricalpower measuring system according to claim 1 wherein said current controlmeans comprises a commutating circuit connected between the currentmeans and the recording means and responsive to the electrical input toshunt said control current away from said recording means when saidelectrical input is above the preselected level.
 10. An electrical powermeasuring system according to claim 1 wherein said current means isresponsive to the load current to produce a control currentsubstantially proportional to said load current.
 11. An electrical powermeasuring system according to claim 10 for measuring energy consumptionin an alternating electrical load circuit also comprising a phase anglemeans for applying an electrical input above the preselected levelduring a selected half cycle of said control voltage to the currentcontrol means.
 12. An alternating electrical power measuring systemaccording to claim 11 wherein said voltage sensing means is responsiveto the load voltage to produce a control voltage substantiallyproportional to said load voltage.
 13. An alternating electrical powermeasuring system according to claim 12 wherein said pulse modulatingmeans is responsive to the control voltage level to shunt the electricalinput from the biasing means and from the phase angle means at a ratesubstantially proportional to said cOntrol voltage level.
 14. Analternating electrical power measuring system according to claim 13wherein said recording means comprises a current measuring andintegrating device.
 15. An alternating electrical power measuring systemaccording to claim 14 wherein said pulse modulating means comprises amultivibrator and shunting circuit connected to pulse modulate theelectrical input from the biasing means and from the phase angle meansby intermittently shunting said electrical inputs at a rate varyingsubstantially proportionally to the average level of said controlvoltage.
 16. An electrical power measuring system according to claim 10wherein said current control means comprises a controllable commutatingdevice responsive to the electrical input and connected to shunt saidcontrol current, and wherein said pulse modulating means is connected toshunt said electrical input at a pulse rate substantially proportionalto the average level of said control voltage.
 17. An electrical powermeasuring system according to claim 16 for measuring energy consumptionin an alternating electrical load circuit also comprising a phase anglemeans for applying an electrical input above the preselected levelduring a selected half cycle of the control voltage to the currentcontrol means.
 18. An alternating electrical power measuring systemaccording to claim 17 wherein said recording means comprises a currentmeasuring and integrating device.
 19. An alternating electrical powermeasuring system for measuring the electrical energy consumed by anelectrical load comprising: a current transformer connected to beresponsive to the load current to produce a control current as anoutput; a current measuring and integrating device connected to receivethe control current; a commutating circuit connected between the currenttransformer and the measuring device and responsive to an electricalinput of one polarity to shunt said control current; a biasing means forcontinuously applying an electrical input having said one polarity tothe commutating circuit; a voltage transformer connected to beresponsive to the load voltage to produce a control voltage as anoutput; a multivibrator shunting circuit having a pulse rateproportional to the level of an input and connected to shunt theelectrical input to the commutating circuit; and a rectifying bridgeconnected to rectify the control voltage and apply the rectified controlvoltage as an input to the multivibrator shunting circuit.
 20. Analternating electrical power measuring system according to claim 19 alsocomprising a phase angle means for applying the control voltage as anelectrical input to the commutating circuit to thereby shunt the controlcurrent during the one polarity portion of said control voltage, andwherein said multivibrator shunting circuit also shunts said controlvoltage.